In general, when metal interconnections are formed in a semiconductor device, an insulating material, e.g., silicon oxide is used for electrical insulation between the metal interconnections serving as current paths. Since a fluorine-doped silicon oxide of such an insulating material has a lower dielectric constant (k) than an oxide that is not doped with fluorine, resulting in a decrease in a signal delay, it is used for an interlayer dielectric material of a semiconductor device requiring fine design rule. However, the doped fluorine atom has excellent diffusivity and thus, may produce a highly corrosive hydrofluoric acid (HF) through its chemical reaction with a hydroxyl group (OH) included in a tetra ethyl ortho silicate (TEOS)-based oxide of an underlying layer, e.g., a capping layer under a metal interconnection. Accordingly, hydrofluoric acid may cause air bubbles to be produced or metals to be corroded. When hydrofluoric acid is used to form predetermined patterns, such a phenomenon as previously described may also happen because a fluorine atom of the hydrofluoric acid reacts with a hydroxyl group included in a TEOS-based oxide.